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/* asyn_read() Author: Kees J. Bot
* 7 Jul 1997
*/
#include "asyn.h"
#include <signal.h>
ssize_t asyn_read(asynchio_t *asyn, int fd, void *buf, size_t len)
/* Asynchronous read(). Try if a read can be done, if not then set a flag
* indicating that select(2) should look out for it. Returns like a normal
* read or returns -1 with errno set to EAGAIN.
*/
{
asynfd_t *afd;
/* Asyn_wait() may block if this counter equals zero indicating that
* all of the asyn_* functions are "in progress".
*/
asyn->asyn_more++;
if ((unsigned) fd >= FD_SETSIZE) { errno= EBADF; return -1; }
afd= &asyn->asyn_afd[fd];
/* If this is the first async call on this filedescriptor then
* remember its file flags.
*/
if (!afd->afd_seen) {
if ((afd->afd_flags= fcntl(fd, F_GETFL)) < 0) return -1;
afd->afd_seen= 1;
}
/* Try to read if I/O is pending. */
if (afd->afd_state[SEL_READ] == PENDING) {
sigset_t mask;
ssize_t result;
int err;
sigemptyset(&mask);
if (sigprocmask(SIG_SETMASK, &mask, &mask) < 0) return -1;
(void) fcntl(fd, F_SETFL, afd->afd_flags | O_NONBLOCK);
/* Try the actual read. */
result= read(fd, buf, len);
err= errno;
(void) fcntl(fd, F_SETFL, afd->afd_flags);
(void) sigprocmask(SIG_SETMASK, &mask, nil);
errno= err;
if (result != -1 || errno != EAGAIN) {
afd->afd_state[SEL_READ]= IDLE;
return result;
}
}
/* Record this read as "waiting". */
afd->afd_state[SEL_READ]= WAITING;
FD_SET(fd, &asyn->asyn_fdset[SEL_READ]);
errno= EAGAIN;
asyn->asyn_more--;
return -1;
}
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